— The new home of Anthem Blue Cross and Blue Shield in Connecticut has a roof of several arches, like a row of miniature Quonset huts, to reflect interior light.

On two sides of the building, floor-to-ceiling windows flood the interior with sunlight. The office floor is actually 18 inches above the concrete to allow central air flow to rise rather than being blasted down from huge tubes in the ceiling. These are a few of the environmentally conscientious ways the building owner designed the 300,000-square-foot facility off I-91 in Wallingford.

Another feature — half eaten hamburgers and leftover salad from the cafeteria is sold as compost to Connecticut farms.

Anthem, the state's largest health insurer covering 1.3 million Connecticut residents, started moving workers to the newly-leased facility in September 2011. First, a group of at least 350 people moved in a year ago to the facility six miles north — and two or three interstate exits away. The rest of Anthem's staff arrived late last month at the venue they call "Campus at Greenhill." It was built to federal guidelines for environmentally-friendly construction, called U.S. Green Building Council LEED certified.

The gleaming complex was a cause for worry five years ago when it was left half completed. Campus at Greenhill was supposed to house Mortgage Lenders Network. The now-defunct MLN failed as part of the subprime-lending crash. MLN closed in 2007, leaving the former building developer, Workstage Connecticut, looking for a different occupant.

"When we first made that fiscal announcement that we were coming to Wallingford, this building was just a shell, originally designed as a call center for a mortgage company — a work site that remained unfinished for more than three years," Anthem CEO David R. Fusco told a conference room full of people celebrating the company's new venue on Thursday.

Workstage Connecticut no longer exists and the Wallingford building is now owned by Gale Development, which leases 271,000 square feet — 90 percent of the total space — to Anthem. A representative for Gale International, Carl Seaholm, declined to say how much it cost to build the office structure. Anthem officials did not disclose the lease terms. They did say it is less than their previous venue, and less than comparable space elsewhere.

The building has an open, roomy feel. Anthem has a workforce of 1,300 that splits time between working at home, in the office or elsewhere. At any given time, Anthem has about 850 workers on site. The desks are open to any employee, allowing them to dial in a personal code to receive calls at any desk. And security lockers allow workers to stow personal belongings on the days they do work in the office.

A smaller part of the building is occupied by Burns & McDonnell New England, an infrastructure construction firm, and a third tenant has signed a lease though the property owner would not name the company.

Anthem wanted to scale back the space it occupied in North Haven, and, in 2007, decided on the former MLN site in Wallingford. Anthem sold its 104 acres and four buildings in off I-91 in North Haven to Quinnipiac University. Anthem then leased space from Quinnipiac as the new venue was renovated.

Quinnipiac plans to make the North Haven site a campus for graduate programs in law, business, medicine, nursing and other programs. The university is investing $100 million total to establish the Frank H. Netter M.D. School of Medicine. The medical school will be on the 104-acre site with four buildings in North Haven that Anthem sold to Quinnipiac in 2007. The insurer leased space from Quinnipiac University with the goal of completely vacating North Haven by 2012.

The 1970s and 1980s buildings in North Haven have been under renovation since March and are expected to be finished by March 2013, said Dr. Bruce Koeppen, dean of the School of Medicine.

This week, Quinnipiac started getting interest from prospective medical students.

"On Monday of this week, the school of medicine was listed on what's called the American Medical College Application Service Website," Koeppen said. "So, if you're a student and you want to go to medical school, you must apply through this website."

Within the first 24 hours, Quinnipiac had more than 200 applicants. The university is accepting applications through Dec. 31, and it will admit 60 students next fall.